Transducers capable of converting energy between mechanical and electrical form have many varied uses. Transducers operative to convert electrical energy into mechanical energy include conventional speakers as well as transducers capable of generating high energy vibrations.
A brief summary of prior art is listed below.
U.S. Pat. No. 4,757,548 (1988) to Fenner, Jr. discloses a speaker system with a dome-shaped enclosure cooperating with the magnet and voice coil to enhance sound waves in an adjacent solid or liquid.
U.S. Pat. No. 3,524,027 (1970) to Thurston et al. discloses a sound enhancement speaker system having a wall mounted speaker. The speaker has a flat base. The magnets are a toroid and a pair of plates. The voice coil is attached to a flat plate which in turn is attached to a screw mounted in the wall.
U.S. Pat. No. 4,399,334 (1983) to Kakiuchi discloses a headphone speaker having a dome shaped diaphragm to amplify the energy of the voice coil.
U.S. Pat. No. 3,567,870 (1971) to Rivera discloses a wall surface sound transducer having a pair of cup-shaped housing members. The active portions of the vibrating surfaces are flat. A flat plate vibrating surface, however, typically exhibits a narrow frequency band response (500-5000 Hz), and exhibits harmonic distortion due to low damping ratios.
U.S. Pat. No. 4,635,287 (1987) to Hirano discloses a vibrating voice coil plate activated by a magnet mounted on a flat plate or a vibrator.
U.S. Pat. No. 4,179,009 (1979) to Birkner discloses a landspeaker mounting assembly for a resonance panel.
U.S. Pat. No. 4,550,428 (1985) to Yanagishima et al. discloses a car speaker in which part of the chassis of a car is used to form a permanent magnetic field.
U.S. Pat. No. 3,987,258 (1976) to Tsutsui et al. discloses a floatable, water proof sound cabinet.
U.S. Pat. No. 4,187,568 (1980) to McMullan et al. discloses an electromagnetic vibrator mounted in a waterbed.
U.S. Pat. No. Re 23,724 (1953) to Seabert discloses an underwater speaker encased in a heavy casing. The diaphragm of the underwater speaker is immersible in water.
U.S. Pat. No. 4,514,599 (1985) to Yanagishima discloses a car speaker mountable upon a car panel in which the car panel is used as a vibrating panel during operation of the car speaker.
U.S. Pat. No. 4,055,170 (1977) to Nohuwra discloses a chair having a vibrating sheet positioned to be in contact with an occupant seated in the chair. A speaker generates mechanical energy which drives the vibrating seat.
U.S. Pat. No. 4,105,024 (1978) to Raffel discloses a pair of vibrator motors mounted inside a furniture frame.
U.S. Pat. No. 2,778,882 (1957) to Pontzen et al. discloses a microphone with a planar diaphragm having both sides exposed to the air which permits enhanced Short range sensitivity.
U.S. Pat. No. 3,384,719 (1968) to Lanzara discloses a set of speakers mounted in a cushioned headrest.
U.S. Pat. No. 2,115,098 (1938) to Engholm discloses a perforated speaker cover which forms a portion of a diaphragm assembly.
Deutsches Pat. No. 2,745,002 (1978) to Nohmura et al discloses a flat plate vibration generator.
Deutsches Pat. No. 2,115,190 (1972) discloses a waterbed having a pump or a speaker which causes generation of pulsed vibrations.
U.S. Pat. No. 3,524,027 to Thurston et al. teaches a flat, plate-type speaker housing. A toroidal magnet and a flat magnet are mounted on the back panel of the speaker housing. The magnets drive a voice coil which is affixed to a flat diaphragm. A spring acts as a damping device for the diaphragm. As the voice coil forces the diaphragm to vibrate, an equal and opposite force causes the magnets and the back panel of the speaker housing to vibrate. All the resultant vibration is transmitted into a bolt fastened in a wall, and the wall resonates with the induced vibrations.
This flat plate type of transducer, however, exhibits only a limited frequency response (500-5000 Hz) and also exhibits harmonic distortion. Harmonic distortions result in the generation of heat energy caused as a result of oscillations of the voice coil in the magnetic field. This heat energy causes heating of the transducer and reduces the life of the transducer.
U.S. Pat. No. 3,567,870 to Rivera teaches a modification to Thurston et al. wherein the speaker housing is modified to include a pair of cup-shaped members. A damping spring required in Thurston is eliminated, and a flatter (more uniform) and wider frequency response is achieved and a reduction of some harmonic distortion is achieved. However, the front and back vibrating speaker housing members are flat. These flat members cause harmonic distortion.
'548 to Fenner, Jr. achieves a higher frequency response (10-30,000 Hz) by using a dome shaped front speaker housing member. Yet, the back speaker housing member remains flat, thereby causing harmonic distortion. Additional harmonic distortion is created by a flat horizontal support member mounted inside the shell shaped speaker housing.
The present invention eliminates all flat speaker housing members. A pair of symmetrical opposing domes comprise the speaker housing. No support member is utilized. Rather, the magnet(s) are mounted directly on the inside of the back dome member. The dome members are rigid, thereby providing a high damping rate without the use of springs. Other design advantages include flatter frequency responses, crush-resistant deep water high pressure housing, crush-resistant load bearing shock absorbing housing useful as shock absorbers, and vibration sensitivity foe active vibration (phase cancellation) applications.